Within such travelling cable support systems, power, such as, for example, electrical power, is passed from an end terminal, by means of conductors which are carried by conductor sleds, to a load, such as, for example, a travelling crane. The conductor sleds are movably carried on a rail, and between the individual conductor sleds and the conductor terminal and the end terminal, traction cords or ropes are provided. These cords or ropes are made shorter in length than the length of the intermediate sections of the conductors so as to ensure that breakage of the conductors, and more particularly, snapping of the individual cores of the conductors, is avoided.
Within conventional travelling cable support systems, the front conductor sled is moved with a relatively high rate of speed. In the case of travelling cranes, on which the conductor terminals are disposed, speeds of more than 4 meters per second may, for example, occur. In order to be able to attain this speed, the travelling crane must, for example, accelerate at a rate of more than 1.0 meter per second per second. When the travelling crane commences movement with such an acceleration rate, and with the cable support system initially in the contracted condition, the conductor sleds disposed behind the travelling crane will be at rest until the traction cord or rope is tensioned. The travelling crane, already moving at a substantial rate of speed, will accordingly suddenly begin to pull the conductor sleds disposed behind it, and this will mean that due to the mass of the next successive sled to be accelerated, substantial disruptive tension forces will be impressed upon the crane and traction rope. More particularly, part of the kinetic energy of the crane will be transferred as kinetic energy to the successive conductor sled which will commence travelling in a sudden manner.
The same process will be repeated when the remaining conductor sleds commence movement. Thus, every time a successive sled begins to move, substantial energy is transmitted from the crane to the particular conductor sled which is to be moved, and as a result substantial disruptive tension forces occur in the traction cords and their attachment means.
In order to reduce the disruptive tension forces which suddenly occur, there has already been a proposal to place spring elements between the points of connection of the traction cords and the respective conductor sleds. When pulling forces are suddenly impressed upon the particular conductor sled, the spring elements extend and the energy then absorbed, and potentially stored thereby, is later converted back into kinetic energy of movement with a corresponding shortening in length of the spring elements. The advantage of this is that the sudden disruptive tensioning forces are reduced, however, it is not possible to avoid the necessity of subjecting the conductor sled to substantial rates of acceleration in order to commence movement thereof. This initial rate of acceleration is dependent upon the mass of the conductor sled which is to be accelerated, and the kinetic energy of movement of the sled or sleds already moving. This means that when each individual conductor sled commences movement, the acceleration of the conductor sleds already moving will be reduced. This, in turn, means that in addition to the occurrence of disruptive tension forces, there is the disadvantage that the extension of the travelling cable support system will take a longer period of time than in an ideal case in which all conductor sleds are started with an acceleration rate which is optimum for the respective individual conductor sleds.